Control system



March 17, 1942. c. G. surrs 2,276,803

CONTROL SYSTEM Filed April 1, 1941 l6 0 l a" 25 2/ 36- JJ 9 v 26 I6 4 J,:9 H p37 Invenbof Cll'waumc'e g (3. Su its,

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Patented Mar. 17, 1942 CONTRUL SYSTEM Chauncey G. Suits, Schenectady, N.iii, assignor to General Electric Company, a corporation of New YorkApplication April 1, 1941, Serial No. sec-s32 (Cl. 1ss 2s) I 7 Claims.

My invention relates to control systems and to a system responsive tothe presence of arcing across a pair of electrodes, and although not,

limited thereto it has application to a control circuit for a fuelburning device.

Oil burner control systems which employ an arrangement for producing anelectric ignition for igniting the combustibies of the furnace, may havean arrangement responsive to a center heat for producing the ignitionand for initiating operation of the electric means for producing thecombustlhles provided that the ignition is functioning properly. In thismanner the combustibles will not be pumped into the furnace ii theignition is not present to ignite them. One method of checking theignition spark includes an arrangement responsive to high frequency impulses which are produced in the ignition circuit if sparking is presentacross the ignition electrodes. Other safety arrangements include flamedetectors for turning ofi the oil burner provided that the flame is notpresent in a predetermined time after the burner has been turned on,such a control system being described in Patent 2,136,256 to Sweet,which is assigned to the same assignee as this present invention.

It is, therefore, an object of my invention to provide an. improved fuelcombustion control system for determining whether a proper spark ispresent across the ignition electrodes.

Another object of my invention is to provide an improved control systemresponsive to a pre determined arcing condition. across a pair or"electrc es,

A further object of my invention is to provide an improved fuel burnercontrol arrangement for initiating operation or the combustible pro=ducing means after it has been determined that a predetermined spark ispresent across the ignition electrodes.

Further objects and advantages of my invention will become apparent fromthe following description referring to the accompanying drawing, and thefeatures of novelty which characterize my invention will be pointed outwith particularity in the claims annexed to and forming a part of thisspecification.

The single figure in the drawing illustrates a control system for an oilburner which is provided with an embodiment of my invention.

In the arrangement illustrated in the drawing, i have provided improvedmeans for detecting the presence ofan arc across the ignition electrodeswhich utilizes the phenomenon that theaction of the are upon aninductive alternating current supply circuit for the ignitiontransformer is such as to produce peak voltages across the transformerprimary in excess of the normal alternating current terminal voltage. Inorder to provide a system responsive to these peak voltages, I connecta'control circuit including an electric discharge device directlyacrossthe primary of the ignition transformer. To detect the peak voltages theelectric discharge device is biased beyond cutoff by a condenser whichis included in the control circuit and is arranged to be charged to thenormal transformer terminal voltage through a half wave rectifier. Thetransformer terminal peak voltages, therefore, are impressed upon thecontrol circuit so as to allow the discharge device to be madeconductive and to operate a suitable relay in the plate circuit toproperly control the fuel burning device, in any suitable manner.

Referring more particularly to the single figure in the drawing, I haveillustrated a control system for a domestic furnace which burns fuel,such as oil, the combustibles being provided at the furnace through aburner arrangement indi cated generally by the numeral iii. This burnerarrangement is of the conventional type and includes an electric motorfor operating a compressor and pump, and an ignition transformer ithaving its secondary or high voltage winding it? connected to arcingelectrodes iii and it, the latter being placed adiacent the nozzle oithe burner arrangement in order to ignite the mix ture of fuel and airas it passes out the needle. motor of the burner arrangement and theprimary or low voltage winding oi" the ignition transformer may beenergized from a source in any suitable manner. Thus, lines and it maybe connected to a suitable source through the line switch it and oneside of the motor of the burner arrangement it is connected to the lineit through a conductor is, while the other side of the motor of theburner arrangement is connected to the line It through a conductor 20,contacts M of a relay indicated generally by the numeral 22, conductor23, contacts 24 of the relay indicated generally by the numeral 25, anda conductor 26 One side of the primary winding ii of the ignitiontransformer may be connected to the line l6 through conductors 21 and28, while the other side of the transformer may be connected to the lineI! through a conductor 29, a reactor 30, contacts 3| of the relay 25 andthe conductor 26. The relay 26 is adapted to be energized upon a callfor heat, which call may be producedin any suitable manner, such as byproviding a suitable condition responsive device, such-as a thermostat32 within the room to be heated. Operating coil 33 of the relay 25 may,therefore, be energized when the thermostat closes its contacts andcalls for heat, and this circuit may be traced from the line l6 througha, conductor 34, thermostat 32, a conductor 35, operating coil 33, and aconductor 36 back to the line ll. It will, therefore, be seen that whenthe thermostat 32 closes its contacts, the relay 25 will pick up andthus energize the ignition transformer. However, the motor of the burnerarrangement ID will not be energized until the contacts 2| are closedupon energization of the relay 22, and this relay is energized upon myimproved control system having determined that a proper spark is presentacross the electrodes [3 v and H.

In order to provide an improved system for detecting the presence of asuitable arc across the electrodes, I employ at detecting arrangementwhich is responsive to peak voltages which are present in the ignitiontransformer primary circuit, these voltages being in excess or the A.C.terminal voltage which is impressed across the lines l6 and I1. Thesepeak voltages result from the action of the are upon the alternatingcurrent supply and apparently arise from the fact that near the currentzero the decrease in conductance due to the arc brings about a rapidchange of current in the reactance of the supply circuit, which isindicated in the diagram as the lumped inductance element 30, leading topeak voltages of short duration. In a low reactance circuit inductancein the form of a reactor 30 may be added to the circuit. These peakvoltages may be detected by any suitable means which are not responsiveto the high frequency character of the generated impulse but only totheir maximum value, and in the illustrated embodiment of my inventionit have provided an 'electron discharge device 3'87 which is allowed tobecome conducting when these peak voltages are present in the ignitioncircuit. This electric discharge device includes an anode 38, a cathode39, and a control electrode 40, and the plate and cathode are connectedin circuit with any suitable device responsive to current passingthrough the plate cathode circuit which may in turn accomplish thedesired control in the fuel burning circuit. The cathode may be suitablyheated by a filament 4| which is connected to a suitable source, such asa secondary winding 62 of a transformer 43. Thus, the cathode 39 andanode 38 are connected in series with an operating winding 4% of therelay 22 through conductors 45 and 45, a secondary winding 41 of thetransformer 43 and aconductor 48. The secondary winding 41 provides thenecessary potential in the anode cathode circuit to produce the flow ofcurrent in the circuit. A. primary winding 49 of the transformer 43 isenergized, when the thermostat 32 calls for heat, through a circuitwhich includes a conductor 58 connected to the line l6 and to one sideof the primary winding,

a conductor which is connected to the other side of the primary windingand which is also connected to contacts 52 of the relay 25, the latterbeing in turn connected to the conductor 26 which connects with the lineH. It is to be understood that any other suitable source of supply maybe provided for producing the flow of current in the anode cathodecircuit. To detect the peak voltages the control tube is biased beyondcutoff by a condenser 53 which is charged the line I! through aconductor 55, a suitable current limiting resistor 55, conductor 29, andreactor 30, contacts 3i and conductor 26. The cathode isconnected to theline l6 and to the other side of the primary of the ignition transformerthrough conductor 48, a conductor 51, capacitor 53, conductors 58 and59, and conductors 21 and 28. The capacitor 53 is shunted by the circuitwhich includes a half-wave rectifier 54 and any suitable source ofsupply such as a secondary winding of the transformer 43. Thus, theplate of the capacitator 53 which is connected to the cathode is alsoconnected to one side of the winding 60 through the conductor 48, whilethe other side of the winding 50 is connected through a conductor 6|,half-wave rectiher 54, conductors 62 and 58 to the other side of thecondenser.

Operation of my improved control circuit is as follows: Upon call forheat, the thermostat 32 will close its contacts thus energizing therelay 25 so that its three contacts 24, 3|, and 52 are closed. .Theclosing of the contacts 3| completes the circuit for energizing theignition transformer H, while the closing of the contacts 52 energizethe transformer 43 which is in the circuit for producing the negativebias on the control electrode. The circuit which includes the burnermotor, however, will not be energized with the closing of the contacts Zl, since the contact 2| of the relay 22 must also be closed before thiscircuit is energized. Before the suitable arcing is present across thearcing electrodes l3 and I4, a charge will be produced on the controlelectrode and make it more negative than the cathode so that no currentwill be allowed to flow in the plate-cathode circuit. Or, two voltageswill be impressed across the control elec trode and cathode in oppositedirections, and one having a sufliciently larger magnitude so that thetube will be non-conducting. When, however, suitable arcing is presentbetween the electrodes l3 and H peak voltages will be produced acrossthe lines 21 and 29 and these lines are in turn connected between thecontrol electrode and the condenser 53 so that these peak voltages willovercome the negative bias on the control electrode and allow it tobecome sufficiently positive so as to permit a current to flow in theplatecathode circuit. When this current reaches a sufficient value therelay 22 will pick up thus closing its contacts 2i and energizing theburner motor circuit.

In view of the foregoing, it will be seen that I have provided animproved arrangement responsive to the presence of an are forcontrolling a fuel burning circuit. My improved control circuit isresponsive to the presence of peak voltages which are in excess of theAx-C. terminal voltages for producing the desired control. Thus, todetect the peak voltages an electric discharge tube is biased beyondcutoff a sufiicient amount. The peak voltages produced by the arc,however, are present in the ignition transformer primary circuit whichis connected between the control electrode and cathode so as to overcomethe biasing voltage which is proportional to or equal to the peak linevoltage, and allow the control electrode to become sufliciently positiveso that a current will flow in the circuit including the plate andcathode. The plate-cathode circuit may be connected in circuit with anysuitable device so as to produce the desired control. In the illustratedembodiment of my invention a relay is which produces a continuousignition, my improved circuit may be applied in an oil burner ignitioncircuit of the intermittent type. It will also be apparent that myimproved control circuit which is responsive to the presence of an arcmay also be employed in an oil burner control circuit which employsother safety mechanisms or arrangements, such as a device responsive tothe presence of a flame and suitable timing mechanism for deenergizingthe burner provided the flame does not appear within a predeterminedtime after the burner is energized. Thus, my arc detection controlcircuit may be employed in such oil burner control circuits as aredescribed and'claimed in Patent 2,058,577 to Eat0n or as described in acopending application Serial No. 347,994, Eaton, filed July 27, 1940,both of which are assigned to the same assignee as this presentinvention. It will also be apparent that although I have described aparticular circuit for producing the negative bias on the con- 'trolelectrode when the arcing is not present and for overcoming thisnegative bias when the arcing is present through the peak voltages, anyother suitable circuit may be provided for detecting the presence ofthese peak voltages which are in excess of the A.-C. terminal voltages.

Modifications of the particular arrangement which I have disclosedembodying my invention will occur to those skilled in the art, so that Ido not desire my invention to be limited to the particular arrangementset forth and I intend in the appended claims to cover all modificationswhich do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent ofthe UnitedStates, is:

v l. A control for a furnace burner having means for producing a flow ofcombustibles to the fura cathode, and a control electrode for energizingsaid electrically operated means, means including a capacitor and arectifier for impressing a charge on said control electrode so as'toprevent a current from flowing in a plate circuit includ-' ing saidanode and cathode, the presence of arcing between said' arcingelectrodes producing voltages across the primary of said transformer" ofa value greater than that of said source, and means for impressing thelast-mentioned voltage on said control electrode in the reversedirection than the biasing voltage so as to allow current to flow in thesaid plate circuit when arcing is present across said arcing electrodes.

3. In combination, a pair of electrodes, means including a transformerfor impressing an alternating potential across said electrodes toproduce arcing therebetween, an electric discharge device having ananode, a cathode and a control electrode, a circuit including acondenser for im- 4 pressing the energizing potential of saidtransformer across said cathode and control electrode, separate meansfor charging said condenser to a potential of substantially thesamemagnitude as said energizing potential but in a fixed direction suchthat no current will flow in the plate cathode circuit of said electricdischarge device, and inductive means in the energizing circuit of saidtransformer for producing a peak voltage in said control circuit inexcess of said transformer en- -ergizing potential in r'esponseto thepresence of a predetermined alternating arcing between said electrodesfor overcoming said condenser potential to allow current flow in theanode cathode circuit of said electric discharge device.

4. A control system responsive to a predetermined arcing conditionincluding a pair of electrodes, a source of alternating potential, meansincluding a transformer having a reactor connected in series with theprimary winding thereof across said source for impressing a higherpotential across said electrodes to produce a predetermined arcingtherebetween, an electric discharge device having an anode, a cathodeand a control electrode, a circuit including a condenser connectedacross the primary winding of said transformer for impressing theenergizing potential of said transformer primary winding across saidcathode and said control electrode,

arcing across said electrodes, an electric discharge device, meansresponsive to the flow oif current through said device for completingthe circuit through said combustible producing means, means for biasingsaid discharge device beyond cutoff, and means responsive to peakvoltages present across the primary of said transan ignition transformerhaving an inductance in the primary circuit thereof for impressing saidpotential across said sparking electrodes when heat from said furnace isdesired, means including an electric discharge device having an anode,

separate means for charging said condenser to bias said discharge devicebeyond cut-oil, means including said transformer and said reactor forproducing peak voltages in said circuit in excess of the potential ofsaid source to overcome the bias of said condenser and allow saidelectric discharge device to become conductive, and means connected incircuit with said anode and cathodeto be responsive to the flow ofcurrent therebetween.

5. A control system for a burner having a pair of ignition electrodescomprising means includ ing a transformer for impressing a potentialacross said electrodes to produce arcing therebetween, an electricdischarge device having an anode, a cathode and a control electrode, acircuit including a condenser for impressing the energizing voltage ofsaid transformer across said control electrode and said cathode, meansfor J of saidcondenser to allow current to pass be tween said anode andsaid cathode when arcing is present between said electrodes, and -meansconnected in circuit with said anode and cathode for controlling theoperation of the burner.

6. A control for a burner having supply means for producing a flow ofcombustibles and a pair of spaced apart arcing electrodes for ignitingthe combustibles comprising means including a transformer ior impressinga high voltage across said electrodes, on electric discharge device hav7 ing an anode, a cathode and a control electrode,

a circuit including a condenser for impressing the energizing potentialof said transformer across said control electrodes and said cathodes,means for charging said condenser to bias said electric discharge devicebeyond cut-off, means including said transformer for producing peakvoltages in said circuit or a magnitude greater than said transformerenergizing potential to overcome the bias of said condenser and allowcurrent to flow between said anode and said cathode, and meansresponsive to the flow of current between said anode and said cathodefor effecting operation of said supply means.

7. A control for a burner having means for supplying combustibles andarcing electrodes for igniting the combustibles comprising meansincluding a transformer for energizing said electrodes to produce arcingtherebetween, and means including an electric discharge device having acontrol electrode energizing circuit connected to be responsive to theenergizing circuit oi said transformer to produce peak voltages in saidcircuit of substantially larger value than said energizing potentialupon the establishment of a predetermined arcing condition between saidelectrodes for effecting operation of said supply means.

CHAUNCEZ G. SUITS.

